What exactly are the rules for how the robber is physicallymoved from hex to hex? The instructions and notes on thevarious cards are a bit ambiguous in this regard. Is therobber constrained to only move to an adjacent hex (orbe blinked back to the dessert)? OR can he be movedmagically to any hex the driver wishes?

the robber can move to any land tile from any land tile. It's not restricted to adjacent tiles and with the latest rules update can even be moved back to the desert. That's the official rules for the robber, but it's fine to play with your own house variant.